Automatic telephone system



April 22, 1930. a. D. WILLIS AUTOMATIC TELEPHONE SYSTEM Original Filed Oct. 1a, 1926 2 Sheets-Sheet 1 IrErE'fiTEF E1 ar'nar'd D M11115 April 22, 1930. B. D. WILLIS AUTOMATIC TELEPHONE SYSTEM Original Filed. 001:. 18, 1926 2 Sheets-Sheet 2 w M w mm u r m A P mom m mm% 7 $0M M N3 mom a known as community automatic exchange Patented Apr. 22, 1930 stares unit BERNARD D. WILLIS, OF OAK PARK, ILIiINOIS, ASSIGNOR T0 AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELAWARE AUTOMATIC TELEEHONE SYSTEM Application filed October 18, 1926, Serial No. 142,267. Renewed July 12, 1929.

This invention relates to automatic telephone systems in general, but is more particularly concerned with small automatic telephone exchange systems comprising relatively few lines; and the object of the invention, broadly stated, is the provision or new and improved automatic switching apparatus which is particularly suitable for use in such small automatic telephone systems, commonly systems.

A articular feature of the invention is a new and improved connector switch which may be operated as an ordinary connector when ext-ending connections to individual subscribers lines, which may be operated as a code-ringing connector to signal a particular party on a party line either on the same line as the calling subscriber or on another party line, or which may be operated to extend a call over an outgoing trunk to some other tele-' phone exchange, such as to the main automatic exchange of a neighboring city. 7

The ObJG-Ct and features of this inventlon M will be described in detail in the following speciucation with the aid of the accompanying drawings comprising Figs. 1 and 2, which, when Fig. 2 is placed to the right of F 1, show by means of the usual schematic circuitdiagrams the principal apparatus to be used in a community automatic telephone exchange In Fig. lot the drawings, the party line comprising conductors 2 and 3 serves the substations A and A. (and others not shown) and terminates at a con'imunity automatic exchange (abbreviated CAX) in the rotary lineswitch RLS. The substations are of the usual auton'iatic type having ringers comprising two coils bridged across the line conductors in series with a three-plate condenser, the third plate of which is connected to ground. The individual line switch RLS is of the usual type, whose operation is well known and together with other rotary lineswitches has access to a ground of connectors, one of which is the connector C shown.

The connector C is of the well known Strowger vertical and rotary type or". switch having a plurality o'thorizontal rows or levels of contacts. The control circuits of the con nector form a particular part of this invention, which Wlll be explained In detail in the following specification. In the banks of the connector C access is had to subscribers"linesin one or more levels, including the party line comprising conductors 102 and 103. I The party line comprising conductors 102 and 103 terminates in the rotary lineswitch RLS (not shown) which is similar to the rotary lineswit-ch RLS and serves substations A and A (and others not shown) which are identical to substations A and A. In a particular level in the banks of the connectors, access ishad to outgoing trunks via repeaters, one of which is shown comprisin conductors 232 connector C, and will be described in detail hereinafter.

The trunk lines extending to the main exchange are two-way trunk lines and also terminate at the CAX in rotary lineswitches for extending calls from the main exchange to the CAX. The trunk line comp ising conductors 232 and 233 terminatesin the R115 which is similar to the rotary lincswitch RLS, and also has access in its banks to the connectors.

With this general description of the object of the invention and the apparatus used at the automatic exchange in mind, adetailed description of the operation thereof will be given. For this purpose it will first be assumed that the subscriber at substation A desires connection with the subscriber at substation A To initiate the call, the subscriberat substation A removes his receiver and dials the number of the line to substa tion A and then dials the code for signalling the subscriber at substation A Responsive to the removal of the receiver the lineswitch RLS rotates its wipers 13, 14, and 15 to hunt an idle connector switch and extend the connection thereto. It may be assumed that the connector C is the one select-ed. When the connector C is seized, a circuit is closed which may be traced frornthe bridge across the line conductors 2 and 3 at the calling station way of armatures 8 and 10 and their working contacts (switching relay 5 operating when the, connector C- 'is seized), wipers 13 and 15, conductors22 and 23, armatures and 47 and their resting contacts, normally closed springs controlled by armatures 58 and 59, through the upper and lower windings of line relay 33 to battery and ground. Line relay 33 operatesand closes a.

circuitior the release relay 34. Release relay operatesand places ground potential on conductor 24 at armature 49, thereby mar ing the c'onnector C engaged, providing a holding circuit for switching relay 5, and

also marking the calling line busy inthe usual manner. At armature a circuit is prepared for the lower winding of switching relay 41; at armature 51 the impulsing path for operating, the magnets of connector C, is prepared. Res onsive tothe dialing of the first digit, line reilay 33 operates and sends a com-esp onding number of impulses to the. vertical magnet 42. The path over which the first of these impulses is sent extends from ground by way of the resting contact and armature 46, armature 48 and the resting contact, armature 51 and the working contact, contacts 7 6, winding of series relay 35, winding of vertical magnet 42to battery; the remaining impulses traverse the same path except that'the cont acts 77 and armature "52 and the working contactare included, andcontacts '76 are excludch thisby reason, ofthe shifting of the off-normal springsupon thelirst vertical step of the switch wipers. Relay 35 1s energizedin se ries with vertical ag-agree, and by reason of'itsslow-acting characteristic maintains its armature52 attracted throughout the send.- ing of this series, The vertical magnet 42 operates responsive to the impulses sent thereto to raisetheswitch wipers 82, 83, and 84 opposite thelevel of bank contacts containing the desired. line. At the termination of thjis seriesfof impulses, relay 35 deenergizes and by releasing its armature 52, extendsthe impulsing path to the rotary magnet 43 by way of armatures (Band 72.

Responsive to the dialing of thenext digit, linerelay 33 again operates and sends a corresponding number of impulses to rotary magnet Relay 40- energizes in parallel withrotary magnet 43, and due to itsslow acting characteristic maintains its armatures attracted throughout the sending ofimpulses thereto. Responsiveto theseimpulsearotary inagnety43rotates the switch wipers 82,83, and 84 into engagement with thebank contacts at which access is had to, thedesired' line, these in this case being bank contacts 92, 93, and 94, respectively.

if the line to substation A is busy at this time, ground potential will be present on bank contact 94. Then when wiper 84 is rotated intoengagement therewith, a circuit is closed for the test relay 39, which includes armature 64 and the working contact, and armature and the resting contact. Test relay 39 will then energize and connect the busy tone current supply to-the lower talking conductor at armature 63 and prepare a locking circuit for itself at armature 61, which circuit is closed when relay 40 dcenergizes and releases its armature 64 at the cessation of the impulses sent tothe rotary magnet. The callingsubscriber, hearing the busy tone, replaces his receiver, initiating the release of the operated switches as will be described later.

It will be assumed, however, that the line comprising conductors 102 and 103 is idle at this time. In this case, relay 39 does not operate and when relay 4O d'eenergizes and releases its armature 64 upon the cessation of impulses to the rotary magnet, a circuit is completed which may be traced from ground by way of the working contact and armature 50 armature 61 and the resting contact, through the lower winding of switching relay 41, closed shaft-springs 80, resting contact and armature 64, wiper 84. bank contact 94, private normal conductor 104, through the winding of the switching relay and winding of the stepping magnetiof the rotary lineswitch RLS (not shown) in series to battery. The. currentflow in this circuit is insufficient to cause the operation of the stepping magnet of the rotary lineswitch RLS, but theswitching relay of the rotary lineswitch RLS isoperated to disconnect the normal ground and battery connections from the lineconductors 102 and 103, and switching relay 41 is operated and performs the following circuit changes: At armature 68 a locking circuit is closed for the upper winding of relay 41. At armature 69 direct ground potential is placed on the test contact 94 and the other contacts multipled thereto to mark the line engaged. A circuit isprepared for relay 39 at armature 70. A circuit is pre pared for relay 37 at armature 71. Rotary magnet 43 is disconnected from the impulsing path at armature 72. A point is opened in the circuit of release magnet 44 at armature 73, A point in the busy tone circuit is opened at armature and at armatures 67 and 7 4 normally open points in the talking circuit are closed.

The line to the desired substation has now been connected with and found idle, so the calling subscriber may now dial the digits to PIOClllCGihi-J code-to signalthe subscriber at substation A Responsive tothe dialing of these digits, relay 40 operates, remaining tures 58 and 59 and the resting contacts,

armatures 67 and 74 and the working contacts, wipers 82 and 83, bank contacts 92 and 93, line conductors 102 and 103, through the coils of the ringers of the substations on this line, through the three-plate condensers to ground. The ringers of the substations on the line operate correspondingto the code produced, a long ring being produced by dial- I ing the digit 8 and a short ring being produced by dialing the digit 2.

To answer the call, the subscriber at substation A removes his receiver, and in so doing places a direct current bridge across the line conductors 102 and 103 which closes a circuit for the battery feed relay 36. this circuit including armatures 54 and 57 and their resting contacts. Relay 36 operates and closes a circuit for relay 39 at armature 53. Relay 39 now operates, closes a locking circuit for itself at armature 60, and disconnects relay 40 from the impulsing path at armature 62, so'that any further manipulation of the dial cannot cause the energization of ringing relay 37. The talking connection is now completed and the two subscribers may now engage in conversation.

At the termination of the conversation, both subscribers will replace their receivers. When the subscriber at substation A replaces his receiver, the circuit of line relay 33 is interrupted. Relay 33 then deenergizes and opens the circuit of release relay 34. Release relay 34 deenergizes and removes ground potentialfrom release conductor 24, thereby opening the circuit of switching relay 5 of the rotary lineswitch RLS and also interrupting the holding circuit of the switching relay 41. relay 34 also closes a point in the circuit of release magnet 44, oft-normal springs 78 having closed upon the first vertical step of the switch wipers. Switching relay 41 deenergizes and restores its armatures to normal, and in so doing closes the circuit of release magnet 44 at armature 73 and disconnects ground trom the test contact 94 at armature 69, thereby marking the line to the substation A idle and also releasing the switching relay of the lineswitch RLS. Release inag et 44 operates to restore the switch wipers of the connector C to normal.

the subscriber at substation A.

In releasing its armature 51,

A subscriber on a party-dine may wish to converse with another party on the same line.

To signal a subscrber on the same line as the calling subscriber, the calling subscriber removes his receiver and dials a special reverting call number, after which he'dials the code digits. of the subscriber with which he wishes to converse. To eXplain'the operations performed, it will be assumed that the subscribor at substation A wishes to converse with The subscriber at substation A first removes his receiver and then dials the digits of the special reverting call number. Responsive to the removal of the receiver, the lineswitch RLS is again operated to :select and extend the connection to an idle connector, which will be assumed to be the connector C. Responsive to the dialing of the digits of the special reverting call number, connector G operates in the manner described above to position the:

wipers 82, 83, and 84 on the contacts of the special number which are contacts 88, 89, and. 90. Of this setof contacts, contacts 88 and 89 are dead, while contact 90 is connected to reverting call; relay 38. After relay 40 releases its armature 64 at the cessation of the impulses ot the second digit, this relay having operated in multiple with the rotary magnet, a circuitis closed which may be traced from ground byway of the working contact and armature 50, armature 61 and the resting contact, through the lower winding of switching relay 41, shaft-springs 80, resting contact and armature 64, wiper 84, bank contact 90, conductor 87, through the windng of reverting call relay 38 to battery. Relay 41'oper- 'ates in this circuit, its useful operations at this time being the closing of the locking circuit for its upper winding at armature 68, the opening of circuit for the rotary magnet 44 at armature 7 2, and the closing of the locking circuit for relay 38 at armature 69. Relay 38 operates and at armatures 58 and 59 prepares a circuit for signalling the desired subscriber over the two line conductors in parallel, and removes the short circuit from the windings of impedance 32.

The subscriber at substation A now dials the code digits to signal the desired subscriber. Responsive to the dialing of these digits. relays 40 and 37 operate as described previously. When relay 37 operates, a ringing circuit is closed'from the generator G over the two sides of the line serving substations A and A in parallel by way of working contacts and armatures 55'and 56, condensers 55 and 56, armatures 58 and 59 and their working contacts, resting contacts and armatures 45 and 47, conductors 22 and 23, wipers 13 and 15, working contacts and armatures '8 and 10, line conductors 2 and 3,- through the two coils of the ringers of the substations on the line to ground. Removing the short circuit from'the windings of operate in. the usualnianner to clos the; impedance 32 includes those windings in series: with the windings of linerelay 33. The windings of the impedance 32 arecumulatively wound; as regards the parallel ringing circuit,xso that the inclusion there'oi in the. bridge across the line conductors prevents all but a negligible amount of ringing currentv from passing toground through the windingsof the line relay 33.

The ring oit the substations. onthe line. respond to the ringing current according to the code dialed. The subscriber at substation A answers the-call by removing his receiver and commencing conversation. Talking. current-is furnished through the windings oi': the impedance 32 and thewindings of the linerelay 3?). The windings of impedance 32, regards the seriewbattery feed circuit. are diii'erentially wound and thus do not niateriallyatlect the line talkingconditions.

At the termination of the conversation both subscribers replace their receivers which initiates the release of the auton atic. switches in the usual manner.

Any subscriber served by the CA may also obtain connection with any subscriber in the distant main automatic exchange over a. trunk ccessiblein the banks oi the connectors. describe the operations performed in setting: up such a connection, it will be assumed that the subscriber at substation A desires connection-with some subscriber in the distant main automatic exchange. To establish this connection, the subscriber atsu-bstation A removes-his receiver, dials one oi the special numbers for outgoing service to the automatic exchange, and then dials the regular directory number of the desired subscriber.

Responsive tothe removal of the receiver at the substation A, the lineswitch RLS- again 0 aeratesto select an idle connector switch and extend theconnection thereto. Aga n it may be assumed. that the connector C is the one selected... Responsive to the dialing. of the first digit of the outgoingservice number, connector C oper t LU raise its wipers opposite the lovel in which the trunks to the main automatic exchange are accessible. Wlhen the wipers are raised to this level, the shaft springs are shi-t'ted,'causing contacts 80 to separate and contacts 79 to close. Responsiveto the dialing of the second digit of the outgoing service number,the connector-C op crates to rotate itswipers 82:, 83, and 84i into engagement with the contactsterminating the trunk. to the. distant main. automatic exchange corresponding to the special number dialed, which in this case it will be assumed. to be contacts 94:, 95, and 96, respectively.

It the trunk line terminating in this set of bank contacts. busy at this time, direct ground potential will be present on the test contact 96 from which the test relay l a loci;-

ing circuit for itself, and; apply the busyv tone to the calling line to inform the calhngsubupon replace his receiver, which initiates-the release of connector C. It -more than one trunk extending to the mainautomaticexchange is provided these other trunks will( also be accessible inthe same level asthefirst trunk. A subscriber, iindmg thefirst busy,

may successively dial the special numbers correspondir 'to these trunkswhich will be known to him. until an idle one is connected with. It a l the trunks to the main automatic exchange test busy, the calling subscriber must await such time when there is one idlc before he can complete the connection.

It will be assumed in this case, however, that the trunk terminatingin the banlc contacts 94:, 95, and'96 isidle at this time. In. this system an idle trunk is markedby the connection of ground potential to the testv contact through a high resistance, so thatthe current iiow through the test relay at the time of testing is insufficient to cause its op.eration. Thus, when wiper 84 comes. incontact with test contact 96, a circuit is closed which may be traced from ground, by wazyoi resistance 219', armature 22 and the resting.- contact, release conductor 204. bank contact' 96, wiper 84. armature 64 and the Working contact, resting contact and armature 70,

through toe winding of test relay 3.) to. bat

tery. Due tov the resistance 219 the current flow in this circuit is insuiiicient tov cause the operation of relay 39. Now when relay 40 releases its armature 5a shortly after the cessation of the impulses of the second digit dialed, a circuit is closed from ground by of resistance 219ftoarmature 64: as previously traced, resting contact of. armature 64,, contacts 79, through the winding of the switchlug-through relay 3l prestingcontact and, armature 62', through the winding of relay 4:0 and the Winding of rotary mag net 43 in. parallel to battery. Due to the coml'ii'ned resistance of resistance 219 and relay 31, the'current flow in this circuit is insuiiicient to cause the operation of relay 40 or magnet 43. Switching-through relay 31 operates, however, and opens the circuit of relay fi l at armature 46. and at armatu-res 4,5 and a7, connects the conductors 22. and 23 directly to wipers 82. and 83, respectively, at the sametime disconnecting the line relay "from in bridge of the the calling lino con.- ductors. Line relay 211 of the repeater'R operates over the circuit including the bridge at the calling station "and the two line conductors in series and closes acircuit for the armature 215. A bridge I release relay 212 at across the outgolng conductors 232 and 23?) is also {)TQTQQEGC at armature 216. Relay 212 operates and places direct groundpo.-

tential 011 release conductor 204 at armature 217, prepares a circuit for the bridging relay 213 at armature 218, and closes a circuit for switching relay 21a at armature 219. In the connector C, the release relay 34 releases its armatures and disconnects ground from release conductor 24 by the disengagement ofarmature 49 from its working contact, ground being immediately reapplied thereto, however, by theengagement of armature 49 with its resting contact via contacts 79 and the resting contact and armature 64.

e In the repeater R, relay 21 1 operates when its circuit is closed at armature 219 and closes a circuit which may be traced from ground by way of the working contact and armature 223, through the winding of switching relay 251 of the rotary lineswitch RLS through the winding of rotary magnet 259 tobattery. Thecurrent flow in this circuit is insufiicient to cause the operation of the rotary magnet, but relay 251 operates and disconnects the normal battery and ground connections from conductors 232 and 233, respectively. At armatures 222 and 221 the bridge across the outgoing conductors 232 and 233 is closed which causes the operation of the line relay in the incoming selector at the main automatic exchangein whichthe outgoing trunk conductors terminate.

The subscriber at substation A now dials th digits of the regular directory-number of the main automatic subscriber. Responsive to the dialing of each digit, line relay 211 deenergizes and reenergizes a corresponding number of times, openin the bridge acrossthe outgoing trunk conductor 232 and 233 at armature 216 a corresponding number of times to operate the line relay of an automatic switch at the main automatic exchange in the ordinary way. Furthermore, at each deenergization, a circuit is closed for relay 213 at armature 215, which relay operates to short circuit the impedance 225 and remove the short circuit from the resistance 226 at armature 220. By reason of the slowacting characteristics of relay 213 and relay 212, these relays remain energized during the dialing ofeach digit. In this manner automatic switches in the main automatic exchange are operated which complete the connection to the called subscriber.

After the connection has been completed and the called subscriber has removed his receiver to answer the call, conversation may take place. At the termination of the conversation, bothsubscribers will replace their receivers Replacing the receiver at substation A opens the circuit of line relay 211 in repeater R. Relay 211 deenergizes and at armature 216 opens the bridge across the outgoing trunk conductors 232 and 233,

thereby causing the release of the automatic switches in the main automatic ex change inthe usual manner; Relay 211 in thereby again marking theline to substation A idle and causing the release of switching relay 5 of the rotary line switch RLS.

Release relay 212 of repeater R in deenergizing, alsoop'ens a point in the circuit of relay 213 at armature 218, andopens the circuit of switching relay 214 at varmature Relays 213 and 214 deenergize and restore their armatures'to' normal. The release of armature 223-opens the circuit of switching relay 251 of therotary line switch R118 Relay 251 then deenergizes and restores its armatures to normal. All the switches are now at normal, and may be taken for use to complete another call. a

As previously mentioned, the trunk lines extending from the O'AX to the main automatic exchange are two-way, and therefore connections may be established from the main automatic exchange to any subscriber in the CAX. To establish such a connection, a calling subscriber first dials a special number to reach the CAX after which he dials the regular directory number of the desired vsubscriber at the CAX, which includes the two line selecting digits and the code selecting digits if the desired subscriber is on a L r party l1ne. W hen a trunk, for example the one comprising conductors 232 and 233, is

seized at the main automatic exchangetor extending such a connection, a bridge is placed across the trunk conductors which cause rotary lineswitch RLS to rotate its wipers in search for a trunk extending to an idle connector. When an idle connector is found, switclnng-relay 251 operates'to extend the connection to the selected connector and places direct ground potential on the test contact 96, and the test contacts multiply connected. therewith, by way 01 release conductor 201 at armature 254:, thereby marl;- ing thistrunk engaged. The seized connector now operates responsive to the remaining digits just as did connector C asdescribed previously. V

A; particular; feature of. the connector'is that should it become desirable to dispense with rotary lineswitches in the C.A.X. (in casethe number oflines'does not warrant their use), the connector C may beconnected directly' to a subscribers line without the addition of any relays or change in the circuits. -When this done, the switching. re-

and battery connections through the line -lav 310i connector C also functions'as a ent- What is thought new and desired to-have protected by Letters Patent will be specifically stated the appended claims.

What is claimed is V 1. In a telephone system, a connector switch, a trunk line terminating in said switch, a calling line, means for connecting said ca-llingline to said switch via said trunk line, a second line, impulsing contacts at a station on said calling line, and means responsive to theactuation of saidcontacts for then operating said switch either to connect with said'second line and signal a subscriber thereon orto signal another subscriber on said calling line via said trunk line.

2. In a telephone system, a connector switch, a trunk line terminating in said switch, a plurality of subscribers lines each accessible in a separate set of contacts in the banks of said switch, a special set of contacts V in the banks of said switch, means controlled connection with said switch Via said trunk over anyone of said lines for establishing a the two sides of the callingline in ser-ies for then operatmg said switch either to connect with said second line and signal a subscriber 1 thereon over the two sides ofsaid second line switch, a calling line and a second line,

in parallelor to signal a subscriber on said calling line overthe two sides of sald'calllng line in parallel.

at. In a "telephone system, a connector switch, a trunk 11116 terminating 111 said means lor connecting said calling line to said switch viaysaid trunk line, means for then operating said switch either to connect with said second line and signal'a subscribe'r thereon or to signal a subscriber-on ,said calling-line, said last meansincluding aline relay-bridged across said trunk line, an

impedance connected in series with said line relayhaving windings differentially wound with respect to the windings-of. said line relay and normally. short-circnited, -a nd; means vfor removingsaid short circuit when a subscriber on said calling line is signalled.

o. Ina telephone system, a subscribers line, a connector switch connected to said line, trunk lines and other lines accessible to said switch, 'meansl'or o'peratmg sald'switch to connect with any one oi said otherlines or said trun'l 'lines, means in said switch operable when a subscribers line is'connecte'd with for applying signalling current to the called line, a single-wound relay in said switch operable when a trunk line is connected with for disabling said signalling means, a second switcii having access to said first subscribers line, means for operating said second switch to connect with said first subscribers line, and means responsive to said connection for operating saidrelay/ 6. In a telephone system, a subscribers line,

a connector switch, trunlrlines and other the trunk linewhen a trunk line isconnected with for disconnecting said linerelay.

in a'telephone system, a connector switch adapted either to be individual to a subscribers'line or to be accessible to a plurality of subscribers lines, trunklines and subscribers lines accessible to said switch, means including a line relay controlled over a calling line for operating said switch to connect withone of said subscribers lines or with one of said trunk lines, a second relay in said switch having a single winding, means for closing circuit for said winding to op crate said second relay when a trunk line is connected with tor disconnecting said li, c relay, and HISQDS OPGIZElJlG in case said connector switch is individual to a subscribers lineior closing a circuit for said winding to operate said second relay when a second connector switch is operated to connect with the subscribers line to which said first connector switch is individual.

8. In a telephone system, an automatic switch, means for directively opera-ting said switch, a first and a second switching relay in said switch, a test wiper for said switch normally connected to a terminalot said first relay, and means responsive to the operation of said switch to a certain extent for discon necting said test wiper from said first rela and co'nnectin it-to a terminal of said second relay.

9. in a telephone system, an automatic CFI lSt)

thereovcr for operating said switch, means in said switch for ringing back over said trunk line, an impedance coil, and means for connecting said coilin series with said line relay during the ringing period.

10. In a telephone system, a trunk line, means for transmitting a series of impulses over said trunk line in one direction and a relay bridged across said trunk line and responsive to said impulses to cause the transmission of ringing current over said trunk line in the other direction during the transmission of said series of impulses.

11. In a telephone system av trunk line means or transmitting impulses over said trunk line in one direction a relay bridged across said trunk lineand responsive to said impulsesto cause the transmission of ring- 7 ing current over'said trunk line in the other direction, and means operated duringthe ringing period for preventing the ringing current from interfering with the operation of said relay.

1?. in a telephone system, means including a connectorswit-ch for connecting a calling subscribers line and acalled subscribers line, means for operating said switch over the twO sides of the calling line in series, and means in said switchforsignalling the called party over the two sides of the called line in parallel. 1 V

13. In a telephone system, a combined connector and ringbacl;- switch, a trunl; line terminating in said switch, andmeans in said switch for operating the same either to signal a called line or to ring back on a calling line over the two conductors of said trunk line in parallel.

14. In a telephone system, a combined connector and ringbac switch, saidswitch being accessible to calling lines and having wipers for connecting to called lines, means in said switch for signalling a called line over a circuit including said wipers, and means controlled by the calling device on a. calling line for signalling the calling line over a circuit excluding said wipers.

15.; In a telephone system, a combined connector and ringback switch, said switch being accessible to subscribers lines and having -wipers for connecting to subscribers lines,

and means in said switch for signalling a called subscriber either over a circuit including said wipers and the two sides of the called line in parallel when the called subscriber is on'some line other than on the calling line or over a circuit excluding said wipers when the called subscriber is on the same line as the calling subscriber.

In a telephone system, an automatic switch and means for operating it, talking conductors extending through said switch and divided into two serially connected sections, a ringing relay in said switch, and means for operating said ringing relay under 'nal rent over the second section to the exclusion of the first. '17. In a telephonesystem, an automatic switch, a trunk terminating in said switch, a called line, calling device for controlling the operation of said switch to connect, under certain conditions, .with said called line, means responsive to the operation of said calling. device when said called line is connected with to signal over the called line, and responsive to the operation of said calling device under certain other conditions to sigback over said trunk.

18. In a telephone system, a trunk line, a line relay adapted to be intermittently operated,responsive to a series of current impulses cent over said trunk line in one direction, and means responsive to the intermittent operation of said relay and efiective throughout a series of impulses for signalling back over said trunk line in the other direction. 7 1 V 19. In a telephone system, a calling sub scribers line, a trunk, means for connecting said line to said trunk, and a signalling device terminating said trunk and controlled over the two conductors of said line in series for signalling back over the two conductors of said trunk in parallel.

20. In a telephone system, a calling line, and means controlled over the two conductors: ot-said line in series for signalling back over the two conductors'of said line in parallel contemporaneously with the exercise of said control.

2i. a telephone system, an exchange, a party line terminating at the exchange, and means at the exchange controlled overzthe two conductors of said line in series from one station on said line for signalling the subscriber at anot-l'ier station on said line over the two conductors of said line in parallel during the time that the control is being I means for establishing a flow of current over the conductors of said line, means at one station on said line for intermittently -inter-.

rupting said current flow, and means for automatically applying a source of signalling currentto-said line while saidinitial flow of current is being intermittently interrupted to signal another station on said line.

24-. In a telephone system, a combination connector and reverting call switch, normally operating as a connectonand a relay responsive tothe' operation of the switch to a particular position for converting it into a re verting call switch. 7

In a telephone system, a trunk having a release conductor, means for placing direct ground potential on said conductor when the trui'ikis busy and for placing ground potential through a resistance on said conductor when the trunk is idle, a switch and means for operating it to connect With said trunk, a busy relay and a switching relay suc- 'vcl-y connected to said conductor when saidconnection is established, said busy test relay being responsive to the presence of direct ground potential on said release conductor to prevent the operation of said switching relay, and said switching relay :ponsive to the presence'of ground g connection over said trunk line. 26; In telephone system, a connector switch having access to both subscribers lines and trunk lines, means for operating said switch, a single set of wipers in said switch for connecting with the bank contacts of said subscribers lines or said trunk lines, talking conductors in said switch, a switchingrelay in said switch for connecting the talking conductors to said wipers, a switching-through relay for connecting the talking conductors to said wipers, means for operating saidfirstrelay in case the Wipers come to rest on the bank contacts of an idle subscri'bers line, and means for operating said second relay in case the wipers come to rest on the bank contacts of an idle trunk line, said relays being operated independent of each other,

the operation of said first relay to connect the talking conductors with said wipers in case the wipers come torest on the bank cont acts of arr idle suhscribers line, means for operating said first circuit and for closing a' p'o'in-t in said" second circuit responsive to the operation of said of trunk lines,- and means for clo mg a seccircuit to cause the operation of said second rel ay'to connect the talking conductors'with wipers in case the wipers conic througl-i' said resistance to complete )ers opposite a group 7 to rest on the bank contacts of an idle trunk line.

28. In a telephone system, a connector switch having access to subscribers lines and to trunk lines through a single set of wipers, means for operating said switch, talking conductors in said switch, a relay operated only in case said wipers connect with an idle one of said subscribe1"s lines, a second relay operated only in case said wipers connect with an idle one of said trunk lines, and contacts on said relays for connecting said talking conductors to said wipers.

29. In a connector switch adapted to extend connections to subscribefis lines or to trunk lines through a single set of wipers, talking conductors, two switching relays for connecting said ta king conductors to the wipers, and means for independently operating either relay depending on the type of line connected with; V

30. Ina switching device adapted to extend connections to two classes of lines through a single set of Wipers, two switching relays for completing talking connections through the wipers, and means for operating one or the other of said relays depending on the class of line connected with.

31. In a telephone system, a trunk comprising two conductors, an impulsin'g circuit including the two conductors of said trunk in series, a signalling circuit including the two conductors of said trunk in parallel, means for simultaneously transmitting impulses over said first circuit and ringing current over said second circuit, and means for preventing interference between said circuits.

32.111 a telephone system, a trunk line, a signal operative responsive to the application of alternating current to said trunk line, an automatic switch, a line relay bridged across the conductors of said trunk line and responsive to direct current impulses sent over said trunk line for controlling the operation of said automatic switch, and means for substantially preventing the passage of alternating current through said line relay when such current is applied to said trunk line to operate said signal.

In witness whereof, I hereunto subscribe my name this 15th day of October, A. D. 1926. r I BERNARD D. VVILL-IS. 

